Vibrator-exciting action



Dc. l2, 1950 B. F. Mn-:ssNER -EXCITING ACTION VIBRATOR Filed July 14,1947 IN'vENTo'R 1121/2 fMzessnez in musical instruments.

Patented Dec. 12, 1950 VIBRATOR-EXCITING ACTION Benjamin F. Messner,Harding Township, Morris County, N. J assigner to Miessner inventions,Inc., Harding Township, N. J., a corporation of New Jersey ApplicationJuly 14, 1947, Serial No. 760,795

10 Claims.

This invention relates to actions for the excitae tion of vibrators,such as the vibrators employed The invention contemplates especially,though not in all aspects limitatively, instruments of the piano type,wherein tuned strings or other Vibrators are percussively excited byhammers under the control of a keyboard. The description willaccordingly be presented largely with relation to a piano.

In United States Patent No. 2,271,469 issued January 27, 1942 on anapplication of; mine, I pointed out the relatively great complexity of amodern action of conventional design-involving, as Ait doer', anescapement mechanism, usually in the form of a pivoted and biased jack,to permit rebound of the hammer from the string to a greater separationlfrom the Vlatter than that to which the hammer had been propelled onits way to the string; a checking mechanism, usually in the form of aback-check, to provide some limitation of the rebound and to assist inthe function of the next-mentioned apparatus; and a repetition-aidingmechanism, typically (in a grand piano action) in the form of aspecially mounted and biased lever, for reducing the extent to which thekey must be released in order to place the action in condition foreffective repetition of key operation.

In that patent I disclosed and claimed an action from which all three ofthe mechanisms just mentioned ,were eliminated, in which the newarrangements introduced were of inherently great simplicity, and yet bywhich excellent and insome respects improved performance was achieved.

In United `States patent applications since led (Serial No. 556,166,filed September 28, 1944 now abandoned; Serial No. 566,979, filedDecember 7, 1944, on which Patent No. 2,469,568 has since been issued;and Serial No. 707,379, filed November 5, 1946) I have disclosedmodiiications of and improvements on the actions disclosed in thatpatent.

While in its broader aspects the present invention has certain featuresin common with the inventions mentioned above, its preferred embodimentsare specifically different therefrom in that they retain the back-checkmechanism of the conventional actionwstill eliminating, however, theescapement and repetition mechanisms.

A prime requirement of a satisfactory actionover and above itselementary one of exciting the vibrator in the iirst place-is that thehammer or other vibrator-exciting member shall be precluded, uponrebounding from'r the vibrator after its original excitation thereof,from rerebounding or bouncing back into a further contact (or series offurther contacts) with the vibrator. In conventional actions thisDreclusion is accomplished by the escapement mechanism, at the expenseof entailing the need for both checking and repetition mechanisms. Inthe inventions mentioned above this preclusion is in generalaccomplished by the use of true viscous energy absorption and/or ofsuitable opposing impacts on the hammer. According to the presentinvention this preclusion is accomplished by a braking effect exerted onthe hammer. Thus it is an object of my invention to achieve, in avibrator-exciting action, a braking of the rebound of the hammer orother vibrator-exciting member sufficient to preclude a further contactof it with the vibrator.

In conventional actions such braking effect as -the back-check may exerton the hammer is a wholly subordinate one, supplementing (for purposesother than further-contact preclusion) the relied-on elect of theescapement mechanism in precluding further hammer-vibrator contact. Itis an object of my invention to use the back-check, or means ofgenerally similar nature, as the prime means of precluding such furthercontacts.

In conventional actions the more effectively the back-check, in itssubordinate role, may have braked the hammer, the poorer tends to be thecondition of the action for any intended repetition of the excitation ofthe vibrator by repeated key operation. vIt is an object of my inventionto utilize the .back-check, or means of generally similar nature, topreclude further contacts of the hammer or other exciting member withthe vibrator, without harmful effect on the repetition. And it is anobject to provide an action with repetition characteristics improvedover those of conventional actions.

It is an object of my invention to achieve, in a vibrator-excitingaction, a dynamic braking of the rebound of the hammer or othervibrator-exciting member from the vibrator-i. e., a braking effectproportional to the need therefor.

It is an object to provide a generally simpliiied and improvedvibrator-exciting action.

Other and allied objects will more fully appear from the followingdescription and the ap pended claims.

In the description reference is had to the accompanying drawing, inwhich:

Figure l is an elevational view of one embodiment of my invention, byway of example in an action for a piano of the grand type;

Figure la is a cross-sectional view taken along the line lezia of Figurei;

Figure 2 is an elevational view of a portion o the apparatus i Figure 1but illustrating the same with the components in positions which theyoccupy at a certain stage during operation;

Figure 3 is a fractional elevational view illustrating a modieation ofmy invention in respect of the hammer structure, it being understoodthat this is capable of optional substitution for a correspondingportion of the structure of Figure 1;

.if-ig. Se is a cross-sectional view taken along the line '3c-ia ofFigure 3; and

Figures li, and 6 are diagrammatic illustrations oi the motions oicertain parts of the apparatus in the illustrated. embodiments of myinvention.

In Figure l the numerals I, 2 and 3 respectively designate the front,intermediate and rear rails ci' the key-assembly portion of the pianoaction. Extending upwardly from the rail 2 is shown a pin fl, encircledby a bushing or pad 5; and a key 5 is shown pivotally assembled on thatpin and resting on that pad. The front end of the key extends over therail I, which is provided with the guide pin 1 extending upwardly andfreely into the key, that pin being encircled by the bushing or pad 8underneath the key. The rear end of the key is shown in its normalposition of rest against the top surface of the strip or pad 5, which inturn is secured on the top surface of the rear rail 3. Between the pivotpin i and the rear extremity of the key, the key 6 is provided with theupwardly extending captan screw iii. The key assembly as so describedwill be recognized as well known.

Driven by the oapstan screw Il), upon operation of the key (i. e.,down-stroke of its forward extremity), is the hammer I I. This may beconsidered as comprising the hammer head I2; the hammer stem I3, at therear end of which the hammer head l2 is attached (in manner hereinaftermore detailedly described); the hammer butt Ed, in which the forward endof the hammer stem I3 is secured; and the pad I6 secured to the lowersurface oi the hammer butt I4. The butt lf2, and thereby the entirehammer I I, is pivoted at il to a flange I8, which in turn is secured toa suitable rail i9 in the action.

The hammer I i is coupled to the capstan screw Iii, so as to be drivenby the key 5, through a suitable coupling member such as 51. This may bein the form of a cylinder, for example of metal, with of its endportions spun over into endclosing formation excepting for a relativelysmall central aperture-as shown in Figure 2 for the upper end of themember 51. In and extending downwardly from the hammer butt I4 throughthe i5, a short distance rearwardly from the pivot I1, there is secureda small pin 53; and in and extending upwardly from the capstan screw iiithere is secured a small pin Ell. The parts are so positioned that thepin 53 is disposed approximately above the pin 54. The coupling member51 may extend from the pad iii to the capstan screw Iii, excepting thata pad 553 ci thin felt or the like may intervene between the bottom ci51 and the top of the capstan screw. The pins 53 and 5d respectivelyextend freely through the respective apertured ends of the couplingmember.

The string which the hammer I I is to strike is shown as 25,horizontally disposed above and in the path of movement of the hammerhead I2 Y end of the key bottoms on the pad 8.

when the hammer pivots about I1. It will be understood that uponoperation of the key 6 the attendant upward movement of the couplingmember 51 will rock the butt Ill upwardly about the pivot I1, carryingthe hammer head l2 toward the string 20.

The capstan screw I5 may be so adjusted that at the conclusion of anabnormally slow operation of the key-i. e., one so slow that thecoupling member 51 remains in contact (through 58) with the capstanscrew and the pad I6 remains in contact with the coupling member-theactive (top) end of the hammer head I2 will have been brought to a smalldistance from the string 2ta distance comparable to that to which in aconventional action the hammer head has been brought at the time oftripping for example.

The normal position of the hammer will be xed by the resting of the buttI4, through pad I5 and coupling member 51, against the capstan screw I0,and the resting of the rear end of the key through pad 9 on the rearrail 3. The downward displacement of this normal hammer position fromthe keystroke-end ,position will of course be determined by the distancethrough which the capstan screw I0 moves during keystroke-and thisdistance of capstan-screw travel is in turn established, asconventionally, by adjustments of the effective thicknesses of pads 8and 5 (as by :choice of the thicknesses of stacks 8a and 5a, of paper orcardboard washers with which fixed-thickness pads 8 and 5 may besupplemented) which adjustments of course iix the length of keystroke(as well as the normal key level).

As a stop against overshooting of the hammer downwardly upon key release(due to momentary yieldings of Various parts such as pads I6, 9 etc.),with consequent strain on the hammer stem I2, there may be provided ontop of the key G-and in the path tending to be traversed by the hammertail I5 hereinafter mentioneda pad 23 of soit felt or the like, of sucha thickness that on downward hammer motion to slightly beyond normalhammer position the lower end of the hammer tail I5 will impinge againstthe pad 23-from which it will, however, normally have a slight spacing.

Simply by way of simplification of illustration, there has been omittedfrom Figure 1 any showing of the usual damper for the string 2i); thismay, however, be provided in any conventional manner.

When the key 6 is operated the hammer will be propelled toward thestring, until the forward At this point the movement of the key and ofthe coupling member 51 will be essentially stopped; in the case ofstronger blows administered to the key, the key and coupling member willcontinue their movements for a small further distance while the pad 8 isbeing compressed to a slight degree, and/or may execute a small furtherexcursion while the upward inertia of the rear po-rtion of the keymomentarily causes a slight lifting of the key from its resting on pad5-but any such continuance or further excursion is at sharply reducedvelocity.

The hammer has been propelled by the coupling member up to the time ofkey impingement on pad 8, and has acquired an upward inertia of its own.At this time, being free to continue its movement, it ceases to bepropelled by the nowstopped or much-slowed coupling member, and moves onwithout discontinuity of velocity to strike the string. It produces aninitial upward deiiection of the string; it then moves downwardly withthe string as the latter accelerates from its deflected position backtoward its normal position, thus starting a rebound from the string.

AsV the string passes through its normal position and decelerates in itsdownward movement, the hammer under its own inertia (as well as gravity)leaves contact with the string and continues its rebound downwardlythrough the small distance required to bring it into impingement againstthe coupling member 5I-assuming the key to have remained in operatedposition since the propulsion of the hammer by it. Of course if the keyhas not remained in operated position (i. e., if it has been releasedpromptly after being struck) the downward passage of the hammer willcontinue through the very substantial distance required to restore it toits normal (Figure 1) position. While it will tend to overshoot thatposition, there have already been described means (i. e., pad 23) forrelieving any resulting strainsand the hammer will be so far from thestring that any re-rebounding toward the string is quite harmless.

If, however, the key has remained in operated position the hammer, uponpassing through the small distance required to bring it into impingementagainst the coupling member 5l, will come into such impingement and willthen, by its inertia, cause a temporary compression of various compliantmembers in the system, including the hammer stem I3, the pad I6, the pad5, and various other compliances (including the equivalent compliance ofthe pad 8 if that is then being compressed by key pressure, in thatthere will be occasioned a temporary de-compression of that pad), thehammer moving downwardly at decreasing velocity while yielding up itsenergy to those compliances. The hammer will then be moved upwardly, bythe release of the energy acquired by those compliances, at a velocitywhich increases until the hammer has reached the point at which it beganthe compression of those cornpliances, by which time all the energy isdelivered to the compliances (reduced only by dissipation therein) willhave reappeared in the hammer in the form of upward inertia.

The foregoing outlines the action of the halm-A mer in the absence ofappropriate counteractive .l

measures. And it will be understood that if such counteractive measuresare not applied, the hammer will respond to its own momentum bycontinuing on toward the string, and will re-strike the string exceptingin the special case of a relatively weak original striking. Uponrebounding from the string after the re-striking, or dropping down againwithout re-striking in the special case just mentioned, the hammer willenter the second cycle of an oscillation to and from the coupling member57 which oscillation may be considered to have begun when the hammerfirst rebounded from the string after the original, intentional stroke.The only limitation of the number of cycles of this oscillation, in theabsence of counteractivemeasures, is provided by the gradual dissipationof energy in the system-and the hammer may re-strike the string in asmany as several of the early cycles of the oscillation. It was toprevent such tonally ruinous occurrences that the escapement mechanismsof conventional actions were resorted to and are still employed.

According to theV present invention I apply a braking force to thehammer during its oscillation to and from the coupling member 51; bysuch application I limit the oscillation, which the hammer of coursestill attempts or tends to engage in, to a harmlessly low magnitude andrapid attenuation. I apply this braking force in progressively greaterdegree the higher the velocity of key operation, with the results notonly that the braking parts are saved from needless wear, but also thatfull reliability of operation is insured. And I limit the application ofbraking force tothe period of attempted oscillation of the hammer, vnotonly avoiding interference with the prior propulsion of hammer tostring, but also leaving the hammer quite unbraked by the time itconcludes its attempted oscillation-with the result that there is nointerference whatsoever (such as occasioned in a convention-algrand-piano action by a tight engagement of hammer-tail with back-check)with immediate repetition.

The braking means according to my invention may typically be formed by aportion of the hammer; an element with which a part of that portion mayenter into impingement at proper times, to result in the frictionalrelative movement which is characteristic of a braking action; and meansfor causing impingement between the elements at the proper times. Thelast-mentioned means may be included in one of the first two elements;it may be responsive to key operation; and in the embodiments of theinvention herein disclosed it has been shown incorporated in the hammer.

In describing the embodiment of Figures 1-2 it is convenient first todescribe the non-hammer element of the braking means. For this I mayconveniently utilize, and I yhave illustrated, a back-check 4@ generallyof the conventional grand-piano type. It will be seen to comprise a rod4I extending upwardly and slightly rearwardly from the rear portion ofthe key 6, a little to the rear of the hammer; a block 42 of wood orother relatively hard material secured on the top extremity of andsupported by the rod 4I; a pad 43. of relatively soft felt or similarmaterial secured against the upper forward portion of the block 42; anda facing 44 of leather or the like secured to the rear-top andforward-bottom portions of the block 2 and encircling the pad 43.

The front surface of the back-check for use in these embodiments ispreferably slightly concave, along an arc centered below the hammerpivot I'I, and the top surface a convex one smoothly progressing, alongan arc formed by a much smaller radius, rearwardly from the frontsurface. The result of this preferred construction is to provide, nearthe top elevational level of the back-check, a horizontal line or narrowregion 4B whose separation from the hammer pivot Il is less than that ofany other portion of the back-check.

The part of the hammer against which the back-check 4!! exerts itsbraking force may be a hammer tail I5, generally similar to thatconventionally provided in grand-piano actions. Such a hammer tail hasbeen illustrated as I5, formed for example in the usual manner by adownward extension of the wooden core of the hammer head I2. While it isnot indispensable, I prefer to incorporate in the hammer tail I5, toform its rear surface, a facing 15a of leather or similar material. Thehammer tail I5 is desirably so shaped `that the bottommost portion ofthe rear surface is rounded off downwardly and forwardly from theimmediately higher portion, which latter may be approximately arcuatelyshaped about the hammer pivot I'I, the two portions merging relativelysmoothly at the horizontal line or narrow region II.

The relative elevations of the regions 40 on the back-check and I I' onthe hammer are preferably so established, by appropriate design of thosetwo elements, that these regions are approximately opposite each otherwhen the key, having been depressed very slowly, is being pressedagainst the pad 8 with force equal to that with which it is so pressedat the conclusion of a relatively strong blow on the key. The relativefore-and-aft positions of the backcheck and hammer are preferably soestablished (and, for example, nely adjusted by bending of the rod 4I)that the path of the back-check region 48 (which pivots about the top ofpad 5) approximately intersects the path of movement of the hammerregion I I (which pivots about I'I) under the same conditions. Theseconditions are those under which the parts assume substantially thepositions illustrated in Figure 2.

The regions 4D and II are those at which impingement occurs atappropriate times between the hammer and the back-check. In theillustrated embodiments the means which causes this impingement at thosetimes is comprised in the hammer I I. It may comprise a exible memberinterposed in the hammer (e. g., in the stem I3), together with the mass(e. g., that of the hammer head and tail I2 and I5) supported by theiiexible member.

In Figures 1 and 2 the material of the hammer stem I3 is shown as brokenjust forward of the hammer head by the short gap Ita. Into the stemportions immediately in front of and behind this gap is inset thehorizontal leaf spring I3b. The hammer head is assembled in the usualmanner on the portion of the stem immediately behind the gap; and" as ameans of positively retaining the assembly of this stem portion, springand head there may be passed through all these elements the pin I3c--asmore fully shown in Figure la. Around the portion of the stemimmediately in front of the gap there may be placed the collar I3d,reinforcing the assembly of the spring in this portion; and through thecollar, stem and spring there may be passed the retaining pin I3e.

It will be understood that the spring I3b between the two portions ofthe stem material constitutes a resilient or flexible portion in thestem; further, that this together with the effective mass of the hammerhead and tail forms a mechanical oscillatory or vibratory system inwhich, after any displacement of the hammer head-and-tail assembly outof its usual angular position relative to the stem, that assembly willtend to vibrate back and forth about that position while resuming it.

The mass of the hammer head-and-tail assenbly, typically centered nearthe center of the head I2, is further removed rearwardly from the pivotEl than is the spring ib. Accor ingl'y when the key is depressed atsubstantial velocity, the inertia of the head I2 will cause the head torock rearwardly about the spring lh, defiecting the latter, while theentire hammer is starting its upward movement toward the string. Thisrearward rocking of the head will continue for an interval determined bythe natural period of the vibratory system abovementioned, whereupon thehead will execute a forward excursion to and past its normal dispositionrelative to the stem,

thus assuming a forward displacement from which it will in turn swingrearwardly again-and so on in a series of excursions which, in theabsence of any other forces on the hammer head tending to modify thatseries, would constitute a. typical train of vibrations eventuallydecaying to zero. The tail I5, and thus the region Il', will execute anentirely similar series of excursions excepting that, since the regionII is .below instead of above the spring I3b, its excursions will at allinstants be opposite in direction to those of the head I2.

Meanwhile the hammer is being propelled toward the string. With atypical adjustment of the parts, including the stiness oi' spring |311relative to the effective mass of the hammer head-and-tail assembly, and`assuming a relatively strong blow on the key, the path of the region II will typically be such as is illustrated by the curve B in Figure 5.In this figure the line AA represents the wholly arcuate path whichwould be followed by the region I I on an upward movement of the hammerunaccompanied by any deection of the spring Ito; the level OO representsthe level of the region II when the parts are in their normal (Figure l)positions; the level KK represents the level at which the region II Ywill be maintained by key pressure against the pad with force equal tothat with which the key is so pressed at the conclusion of a relativelystrong blow; and the level ESS represents the level oi the region il atthe time of original striking of the string by the hammer.

This Figure 5, as well as the corollary Figures 4 and 6, are severaltimes enlarged relative to the structural views of Figures l and 2.

The typical path B in Figure 5 shows that. upon the relatively strongkey blow which it represents, the region II will rise in a path whichfor a substantial distance digresses forwardly from the slow-motion pathAA, and which then re-approaches the latter path but does not reach ituntil the region II' is above the level KK. Then crossing theslow-motion path (and thus ending the rst half-cycle of the swing) thepath B reaches the level SS and perseveres above it (representingdeflection of the string); it is then deilected downwardly (representingthe beginning of hammer rebound) while still at approximately maximumdisplacement rearwardly from the slow-motion path AA. Now representing asomewhat slower hammer motion, the path B re-crosses the path AA (endingthe second halfcycle oi swing) to digress again forwardly therefrom, andto pass below the level KK (representing lmpingernent of the hammeragainst the coupling member 5l and compression of the severalcompliances as mentioned above). As it re-appreaches the path AA itstarts an upward movement (representing the beginning oi' hammerrerebound). Crossing the path AA (and ending the third and entering thefourth half-cycle of swing) it digresses again rearwardly whileexecuting a passage again above the level KK, after which it is shownagain approaching the path AA and reverting toward the level KK, andcoming to an end at the intersection of that path and that level.

The terminal portion of the path B reflects the effect of the back-check4Q on the motion of the region Il' (i. e., on the motion oi the hammerhead-and-tail assembly). 1t is therefore helpful to refer at this pointto 1Figure 4, wherein the path C is that of the region dil on theback-check during the key-blow.

The path C begins at the point Q, representing the normal (Figure 1)position of the backcheck region 40. From Q it extends in a longradiusarc to intersect the path AA at approximately the level KK-whichintersection at that level is the result of the preferred relativepositionings of the regions 40 and I I set forth above, and correspondsto the illustration of Figure 2. The line JJ indicates the approximatelevel at which the region 40 will have arrived when the key firsttouches the pad 8; it is thus at substantially this level JJ that therebegins a deceleration of the motion of the back-check and its region40', which deceleration continues until'the region 40 comes to rest atthe level KK.

The illustrations in Figures 4 and 5 of course do not in themselvesexpress time. It will be understood, however, that at the time theregion 40' has reached the level JJ, the region Il will have approachedthe level KK; that at the time the region Il has reached the level KKthe region 40 will have progressed only part-way from level JJ towardlevel KK; and that by the time the region 40 has reached the level KKthe region Il' will have progressed a considerable distance above thatlevel.

Subject to slight modifications which will be understood to beestablished in any individual case by the particular Vconfigurations ofthe surfaces of back-check and hammer tail adjacent the regions 40 andll respectively, the criterion for non-impingement between those regionsis that the hammer-tail region Il (whose path is B, Figure 5) shall notat any instant lie, in the space system illustrated in each of Figures 4and 5, in a position which is both (1) at any level from slightly aboveto substantially below the level at which the back-check region 40 thenis, and (2) further separated leftwardly from the path AA than theback-cheek region 40' then is. Reference to Figures 4 and 5 inthemselves shows that prior to the fourth half-cycle of vibration thereis no possibility of impingement between the two regions, and thattherefore the original trip of hammer to string is unimpeded-and theconsiderations set forth in the preceding paragraph provide anadditional, though unnecessary, margin of safety against suchimpingement. Y

But in the terminal portion of the path B of the hammer region l I inFigure 5not traversed, of course, until after the back-check region 40'has reached the intersection KK-AA-the criterion for non-impingement isobviously violated. This violation begins at the beginning (designatedas X) of the fourth half-cycle of swing. When the hammer region I lreaches this point the rear surface of the hammer tail l5 a little abovethe region ll will impinge on the back-check region 40. As the upwardhammer movement shown from point X continues, the rear surface of thehammer tail will be dragged along the back-check region iV-the leathersurfaces-of the two, and to a greater degree the underlying felt 43 ofthe back-check, yielding slightly under the pressure of the two elementsagainst each other. This provides a high degree of damping of thererebound of the hammer from the coupling member 51 and, by the time thehammer region Il" reaches the level KK, will have largely used up theenergy of the hammer. At that time the hammer will typically have left aslight amount of energy, and so will pass upwardly slightly beyondcoincidence of region .40' with level KK 10 (and may even momentarilybreak the engagement of hammer tail with back-check) the ham- -merwillhave by no means enough energy, however, to progress far toward thestring, and so will drop back to a position of rest, or substantialrest, of the region 4Q' at the intersection KK-AA.

It is to be noted that at this time the criterion for non-impingement isagain met and the elements, though typically just touching, will not beexerting any restraint on each othera feature important for perfectionof repetition.

A typical operation of the action has been illustrated in Figure 5 anddescribed above for the case of a relatively strong blow on the key.With weaker key blows the nature of the path of hammer region Il willshift somewhatin general, so that the first half-cycle of vibration willend at lower level than in Figure 5, and ensuing half-cycles will bealtered attendantly (and their number in cases incre sed). But I havefound uniformly that an action according to my invention which functionseffectively with relatively strong key blows and resulting highvelocities, functions effectively throughout the range of lower ones.Several factors contribute to this result, among them the sharplyreducing amplitudes of vibration with reducing velocities; thesubstantial safety margin (unused at strong key blows in the case of theFigure 5 path, as above noted) as to unwanted interference with originalhammer movement to the string; the sufficiency of lighter impingements,in whatever cycle occurring, to damp the hammer oscillation, the lowerthe hammer velocity; and, importantly, the reducing need (which reacheszero with still-finite key velocities) forhammer-oscillation-counteracting measures, the lower the hammervelocityresulting from the relative harmlessness of a hammer oscillationto and from the coupling member so long as it is of a low enoughmagnitude to insure positively the absence of any re-striking of thestring.

It is to be understood that even for strong keyblows the shape of thepath of the hammer region l i may vary very considerably from that shownin Figure ll, without harmful effect or departure from the principles ofmy invention. Thus in Figure 6 I have illustrated the path of the hammerregion Il in an action differently adjusted-for example, with a stifferspring i3?) in the hammer stem i3, resulting in a shorter natural periodof vibration of the hammer head-and-tail assembly (the stiffness of thisspring, or the equivalent member, being understood to be acharacteristic which should be related to the particular hammer withwhich it is to be used to produce the desired natural period).

In Figure 6 the path of the hammer region Il' is designated as D. Itshows the path reaching a maximum forward displacement from theslowmotion path AA slightly less than that of path B of Figure 5, butcrossing the path AA (and ending the first half-cycle) at a levelsomewhat below KK. The curve D reaches the level SS at approximately itsmaximum displacement rearwardly from the path AA, and goes beyond SSduring string deflection. By the time the string has returned to itsnormal position the curve D has passed into the third half-cycle; thisit completes while the hammer is engaged in compressing the severalcompliances after impinging on the coupling member 5l. That compressioncontinues somewhat after the curve D has passed into the fourthhalf-cycle, in the remainder of which the curve D comes to itsconclusion at the 'intersection KK--AA, representing the coming to rest(or substantial rest) of the hammer.

It will be recognized that with the path D the criterion fornon-impingement is still not viflated during the original trip of thehammer to the stringthough the safety margin is only a fraction of thatwhich existed in the case of the curve B of Figure 5. The braking actionis still performed, however, with full effectiveness-in this instancethroughout the entire fourth half-cycle, during all of which thecriterion for non-impingement of the regions 4G and Il is violated veryeffectively.

'Ihere are intended no unnecessary limitations as to various features ofmy invention, or to the characteristics of the particular element pathswhich i have illustrated by Way of example in Figures 5 and 6. rhus iorexample While I nd it thoroughly satisfactory to make the fourthhalf-cycle of vibration the one in which the impingement and the brakingaction occur, another half-cycle or a group of half-cycles mayalternatively be selected for use. Again., for example, I may otherwiseprovide the flexible or resilient member in the means which brings thebrake into play. Such a variation I have illustrated in Figures 3 and 3awherein, instead of forming a stem I3 in two spring-joined sections, Iemploy the integral stem I3 very substantially thinned (by removing topand bottom material from an originally circular stem) at the region I3closely adjacent the hammer head; if desired, this region i3 may bejoined to the hammer butt I il' by a stem section i3" along which theoriginal stem diameter is only progressively restored.

These and other modifications which will suggest themselves to thoseskilled in the art Will not necessarily involve departure from thespirit of my invention, the proper scope of which I undertake to dennein the appended claims.

I claim:

l. In a key-operated action for exciting the vibrator of a musicalinstrument, a hammer movable to strike the vibrator; means, moved by thekey in a hammer-propelling path and retained in a limiting position inthat path While the key remains operated, for propelling the hammertoward the vibrator, to and from which means While in that position thehammer attempts to oscillate after striking the vibrator; normallyinoperative means for braking the hammer; a flexible member included insaid braking means to permit its establishment in operative condition;and inertia means included in said braking means and cooperating withsaid flexible member to maintain the braking means in inoperativecondition during hammer propulsion but to place the braking means inoperative condition during such attempted hammer oscillation.

2. In a key-operated action for exciting the vibrator of a musicalinstrument, a hammer element movable to strike the vibrator; means,moved by the key in a hammer-propelling path and retained in a limitingposition in that path While the key remains operated, for propelling thehammer element toward the vibrator, to and .from which means while inthat position the hammer element attempts to oscillate alter strikingthe vibrator; a back-check element moved, normally free of interferencewith the hammer element, by the key; a iiexible member included in oneof said elements to permit impingement between said elements; inertiameans included in said one element and cooperating with said flexiblemember to maintain said elements free oi each other duringhammer-element propulsion but to cause impingement between said elementsduring such attempted Vhammer-element oscillation.

3. In a key-operated action for exciting the vibrator of a musicalinstrument, a hammer element moved by the key, upon operation of thekey, to strike the vibrator; a back-check element moved by the key inproximity to the hammer element; and a resilient member included in oneof said elements and supporting a portion thereof and forming With saidportion a vibratory system placed in vibration by the key upon operationthereof, said elements and their paths of movement being disposedrelatively to each other to cause impingement between said elementsduring an excursion of said system opposite to the excursion initiallyoccasioned by key operation.

4. In a key-operated action for exciting the vibrator of a musicalinstrument, a hammer element moved by the key, upon operation of thekey, to strike the vibrator; a back-check element moved by the key inproximity to the hammer element; and resilient member included in one ofsaid elements and supporting a portion thereof and forming with saidportion a vibratory system placed in vibration by the key upon operationthereof, said elements and their paths of movement being disposedrelatively to each other to cause impingement between said elements tooccur for the irst time following key operation in the fourth half-cycleoi vibration of said System occasioned by that operation.

5. In a key-operated action for exciting the vibrator of a musicalinstrument, a hammer moved by the key, upon operation of the key, ltostrike the vibrator; a resilient member included in said hammer andsupporting a portion thereof and forming With said portion a vibratorysystem placed in vibration by the key upon operation of the key; and anelement positioned to be impinged on by a part of the hammer during anexcursion of said system opposite to the excursion initially occasionedby key operation.

6. In a key-operated action for exciting the vibrator of a musicalinstrument, a hammer moved by the key, upon operation of the key, tostrike the vibrator; a resilient member included in the hammer andsupporting a portion thereof and forming with said portion a vibr-atorysystem placed in vibration by the key upon operation of the key; and anelement positioned to be impinged on by a part of the hammer for the rsttime following key operation in the fourth half-cycle of vibration ofsaid system occasioned by that operation.

7. In a key-operated action for exciting the vibrator of a musicalinstrument, a hammer movable to strike the vibrator; means, retained ina hammer-propelling path and limitedly moved therein by the key, forpropelling the hammer toward the vibrator, to and from which means whilein the position to which it has been moved by key operation the hammerattempts to oscillate after striking the vibrator; an element past whicha part of the hammer moves; and means, included in said hammer andcomprising a flexible member and mass supported by said member, forcausing said hammer part to impinge on said element during suchattempted hammer oscillation only.

8. In a key-operated action for exciting the vibrator of a musicalinstrument, a hammer movable to strike the vibrator; means, moved by thekey in a hammer-propelling path and retained in a limiting position inthat path while the key remains operated, for propelling the hammertoward the vibrator, to and from which means while in that position thehammer attempts to oscillate after striking the vibrator; an elementpast which a part of the hammer moves at least substantially freely whenthe key is operated at low velocity; and means, included in the hammerand rendered effective by the key upon operiation of the key at highervelocities, for causing said hammer part to impinge on said elementduring such attempted hammer oscillation.

9. In a key-operated action for exciting the vibrator of a musicalinstrument, a hammer movable to strike the vibrator; means, moved by thekey in a hammer-propelling path and retained in a limiting position inthat path While the key remains operated, for propelling the hammertoward the vibrator, to and from which means while in that position thehammer attempts to oscillate after striking the vibrator; an elementpast which a part of the hammer normally moves with at least substantialfreedom; a flexible member included in the hammer to permitdisplacement` of a. portion thereof laterally from its normal path ofmovement; and intertia means in- 14 eluded in the hammer and cooperatingwith said ilexible member to maintain said hammer part free of saidelement during hammer propulsion but to displace said hammer part intoimpingement against said element during such attempted hammeroscillation.

10. In an action for exciting the vibrator of a musical instrument, ahammer comprising a hammer head adapted to strike the vibrator, a stempivotally supported at one of its ends and carrying said hammer at itsother end, and flexible means interposed in said stem adjacent to saidhammer head.

BENJAlVIIN F. MIESSNER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 25,305 Marschall Aug. I30, 18591,097,083 Darley May 19, 1914 1,806,595 Cameron May 26, 1931 2,214,112Schulze Sept. 10, 1940 2,280,982 Schulze Apr. 28, 1942

